Method for the control of biofouling in recirculating water systems

ABSTRACT

A method of controlling biofouling in an aqueous system comprising introducing into the system a biocidally effective amount of a water soluble perhalide of the formula: ##STR1## where R 1  and R 2  are hydrogen, hydroxyethyl, alkyl, cyclic alkyl, (alpha, omega)-alkyl, alkyl ether, polyether, heterocyclic ring-substituted alkyl, and halogenated alkyl; n is 2 to 6: X is chlorine, bromine or iodine; and only one of R 1  and R 2  may be hydrogen.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention discloses a novel method for the substantialelimination of the major cause of biofouling in recirculating watersystems, in particular, those systems recirculating water for coolingpurposes, such as, for example, water cooling towers, air conditioningsystems, and the like.

2. Description of the Art

Biological fouling of circulating cooling water systems is a commonproblem resulting from excessive growth and development of differenttypes of simple life forms (e.g., microorganisms such as algae, bacteriaand fungi.) Circulating cooling water systems are excellent places forthe incubation and growth of biological organisms because such systemscontain nutrients (typically organic contamination) from air drawn intothe system and from organic materials naturally occurring in the water.In addition, the water temperature in cooling towers is warm enough toprovide an ideal incubation environment. Biological growth can foulpipelines, increase water circulating costs, cause and/or acceleratecorrosion of metal, attack wood, and substantially reduce heat transferthereby contributing to decreased efficiency of the cooling towersystem.

Common forms of microorganisms found in a cooling tower system includealgae, slime-forming fungi and bacteria, wood destroying organisms andsulfate reducing organisms along with many other forms of bacteria whichmay have little or no effect on cooling tower efficiency.

It is generally desirable that a biocide meet the following criteria:

(1) wide kill spectrum--the agent should be effective against a widevariety of microorganisms, such as, for example, algae, bacteria, fungi,mold and other aquatic organisms;

(2) fast rate of kill;

(3) low cost;

(4) useful in wide pH ranges;

(5) non-corrosive to metals and wood;

(6) compatible with commonly used cooling water treatment chemicals suchas scale inhibitors and corrosion inhibitors:

(7) unaffected by organic contaminants or nitrogen compounds in thewater recirculating system;

(8) ease in handling and application; and

(9) capable of obtaining appropriate federal and state governmentalagency approval.

Biocides can be divided into two basic classifications: non-oxidizingand oxidizing biocides. In general, the non-oxidizing biocides functionprimarily by altering the permeability of the cell walls of themicroorganisms and interfering with their biological processes. Commonnon-oxidizing biocides include organo-sulfur compounds, quaternaryammonium salts, chlorinated phenolics and heavy metal compounds.

Oxidizing biocides cause irreversible oxidation/hydrolysis of proteingroup in the microorganism and of the polysaccharides that bind themicroorganisms to the surfaces of the cooling tower equipment. Theresult of this process is a loss of normal enzyme activity and celldeath.

Oxidizing biocides heretofore proposed for cooling water use include:

(1) Chlorine;

(2) Bromine;

(3) Chloroisocyanurates;

(4) Chlorine dioxide;

(5) Hypochlorites;

(6) Bromine chloride and bromine-chlorine mixtures;

(7) 1-bromo-3-chloro-5,5-dimethylhydantoin ("BCDMH")

Each of these common biocides will be briefly discussed.

(1) Chlorine

Chlorine is probably the most common biocide in use for cooling towertreatment. It is generally an excellent algicide and bactericidealthough some strains of bacteria can develop chemical resistance tochlorine. Often chlorine must be used in a shock treatment system toprovide good biocide performance. Gas chlorination equipment is costlyand generally requires a relatively large capital investment. Normal uselevels must be dramatically increased to maintain effectiveness whencooling water has become contaminated with hydrocarbons, ammonia andorganic material.

Excessive chlorine concentrations have an adverse effect on coolingtower wood. Chlorine also tends to lower pH by its formation of HCl inwater. Chlorine becomes less effective as a biocide above about pH8.0-8.5 and becomes corrosive below about pH 6.5. Chlorine is a heavygreenish-yellowish gas with a suffocating odor. It requires specialheavy and cumbersome steel cylinders under pressure to be transported.The recent industrial concern about industrial leaks and safety havemade handling of chlorine cylinders even more suspect.

(2) Bromine

Liquid bromine has also been used in the treatment of biofouled coolingtowers. However, bromine has not received widespread commercialacceptance, apparently because of handling difficulties and the cost ofbromination equipment, as well as its low solubility in H₂ O. (3.43g/100 g water @ 30° C.)

    ______________________________________                                        Vapor Pressure of Bromine:                                                            °C.                                                                         (mm Hg)                                                          ______________________________________                                                20   173                                                                      25   214                                                                      30   264                                                              ______________________________________                                    

(3) Chlorine Dioxide

Chlorine dioxide is usually classified as an oxidizing biocide althoughits kill mechanism is not oxidative. It is more effective at a higher pHor in nitrogen or organic contaminated systems than chlorine. Because itis an unstable compound, it is usually generated on-site with specialequipment. It is also more expensive than chlorine.

(4) Chloroisocyanurates

Chloroisocyanurates are easily handled powdered compounds whichhydrolyze in water to slowly release chlorine and cyanuric acid.However, they suffer all the drawbacks of chlorine in pH effectivenessranges and present potential corrosion problems.

(5) Hypochlorites

Sodium and calcium hypochlorites function in much the same manner aschlorine gas but in an easier to handle form. However, hypochloriteshave all the disadvantages of chlorine plus a higher cost. Theseproducts also tend to increase pH by the formation of metal hydroxidesand additional reagents must be added to achieve control. There is alsoa concern of quick gassing when product is added to water. Liquidhypochlorites also suffer from quick decay rates of active agent becausethey are unstable.

(6) Bromine Chloride and Bromine-chlorine Mixtures

Bromine chloride, available only as a liquid under pressure, has foundsome favor as a biocide. It hydrolyzes completely in dilute aqueoussolutions to hypobromous acid (HOBr) and hydrochloric acid (HCL). Thehypobromous acid is an effective, potent biocide for algae and bacteria.Bromine chloride has generally not been promoted for use on industrialrecirculating cooling towers because of the high cost for feed equipmentand accessories. Mixtures of bromines and chlorine have also beeninvestigated as biocides. Such mixtures may be applied as a liquid/gasmixture or in the form of sodium hypochlorite and sodium hypobromite. Ithas been reported that a bromine/chlorine mixture displays greaterbiocide activity than bromine or chlorine alone. The costs of handling,as well as the safety issues involved with such mixtures have prohibitedtheir widespread use.

(7) BCDMH

BCDMH serves as an excellent biocide in recirculating cooling towers andother water systems. Its solid form makes it easy to handle and clean-upafter, and its predominate use of bromine chemistry makes it veryefficient where chlorine is not. However, there are certain conditionswhere BCDMH has limitations. The product has low solubility in coldwater, requires specialized feeding equipment to optimize productdissolution and requires high pressure or expensive options to theequipment for large applications.

DISCUSSION OF BROMINE CHEMISTRY

Aqueous bromine has been proven to be a very effective biocide,particularly under alkaline (high pH) and high nitrogen concentrationconditions. A brief discussion of the chemistries involved follows:

A. Bromine and chlorine hydrolyze in water according to the following:

    Br.sub.2 +H.sub.2 O⃡HOBr+H.sup.30 +Br.sup.-    ( 1)

    Cl.sub.2 +H.sub.2 O⃡HOCl+H.sup.+ +Cl.sup.-     ( 2)

Hypobromous acid (HOBr) and hypochlorous acid (HOCl) are the activebiocides.

B. Under alkaline conditions the following reactions occur:

    HOBr→H.sup.+ +OBr.sup.-                             ( 3)

    HOCl→H.sup.+ +OCl.sup.-                             ( 4)

Both HOBr and HOCl are many times more effective biocide then theircounterparts OBr⁻ +OCl⁻.

Table 1 shows the relative concentrations of the hypohalous acids as afunction of pH.

                  TABLE 1                                                         ______________________________________                                                       %       %                                                      pH             HOCl    HOBr                                                   ______________________________________                                        6              97      100                                                    7              76      98                                                     7.5            50      94                                                     8              24      83                                                     8.5             9      60                                                     9               3      33                                                     ______________________________________                                    

C. Bromine and chlorine also differ in their reactions with nitrogencompounds. Both form haloamines (bromamines and chloramines) accordingto the following reactions:

    HOBr+NH.sub.2 X→NBrX.sub.2 +H.sub.2 O               (5)

    HOCl+NH.sub.2 X→NClX.sub.2 +H.sub.2 O               (6)

Chloramines are very poor biocides relative to hypochlorous acid.Bromamines on the other hand, are known to be almost as effective ashypobromous acid. An added benefit for environmental discharge concernsis that residual bromamines have a half life measured in minutescompared to many hours for chloramine.

Morton, U.S. Pat. No. 3,152,073 describes the use of tetramethylammoniumchlorodibromide in sterilizing water. Morton goes on to disclose a widevariety of tetraalkylammonium polyhalides which contain alkyl groups ofsix or fewer carbons, suggesting that they may be used as singlereagents, directly added to water, to achieve sterilization. It has nowbeen found that, in fact, many of Morton's compounds are notsufficiently soluble in water for use by the method disclosed.

Gannon, et al., U.S. patent application Ser. No. 048,902, filed Apr. 20,1987, discloses water sterilization compositions and methods usingtetrasubstituted ammonium perhalides and certain trisubstituted aminehydrotribromides. The utility of these compositions and methods has beeninhibited by the poor water solubility of the compounds.

Accordingly, a primary object of the present invention is the provisionof method of water treatment involving the use of a novel biologicalcontrol agent, or biocide which displays unique qualities when comparedwith other available biocides.

Another object is to provide a method of the character described thatobviates the disadvantages of prior agents.

A further object is to provide a method of the character described whichemploys a novel stable, water soluble source of bromine.

SUMMARY OF THE INVENTION

The foregoing and other objects, advantages and features may be achievedwith a novel method for treating biofouling problems inherent inrecirculating water and other aqueous systems involving treatment ofaqueous systems by introducing a biocidally effective amount of a watersoluble organic ammonium perhalide of the formula: ##STR2## where R₁ andR₂ are independently hydrogen, hydroxyethyl, alkyl, cyclic alkyl,(alpha, omega)-alkyl, alkyl ether, polyether, heterocyclicring-substituted alkyl, and halogenated alkyl; X is chlorine, bromine oriodine; n is 2 to 6; and only one of R₁ and R₂ may be hydrogen,

into the water at a frequency, duration and concentration sufficient tocontrol biofouling. Preferably, the perhalide is introduced in amountssufficient to kill biofouling microorganisms at film forming surfaces ofthe system and thereafter to maintain the concentration of organicammonium perhalide at a level sufficient to reduce substantially theregrowth of such microorganisms at such surfaces. Preferably, theorganic ammonium perhalide is provided at a daily level of at leastabout 0.005 pound per thousand gallons of water in the system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the present invention it has been discovered thatorganic ammonium perhalides effectively control bacterial growth incooling tower, water recirculating and other aqueous systems. By thepresent method, reduction in treatment costs (when compared to the priorart biocidal agents) may be achieved. Due to the nature of water coolingtowers and recirculating systems in relation to microorganism growthenvironments, it is necessary to provide a method of treating therecirculating water which, on the one hand, kills microorganismsadhering to the walls and other structures of the system and, on theother hand, substantially reduces the potential for microorganismregrowth.

Accordingly, the method of the present invention involves treatingaqueous systems by introducing a biocidally effective amount of a watersoluble mono- or di- substituted ammonium perhalide of the formula:##STR3## where R₁ and R₂ are independently hydrogen, hydroxyethyl,alkyl, cyclic alkyl, (alpha, omega)-alkyl, alkyl ether, polyether,heterocyclic ring-substituted alkyl, and halogenated alkyl: X ischlorine, bromine or iodine; n is 2 to 6; and only one of R₁ and R₂ maybe hydrogen,

into the water at a frequency, duration and concentration sufficient tocontrol biofouling in the system.

Preferably, the perhalide is introduced in amounts sufficient to killbiofouling microorganisms at film forming surfaces of the system andthereafter to maintain the concentration of organic ammonium perhalideat a level sufficient to reduce substantially the regrowth of suchmicroorganisms at such surfaces.

The water soluble organic ammonium perhalides that are useful inaccordance with the method of the present invention are disclosed andclaimed in copending Favstritsky, U.S. patent application entitled WATERSOLUBLE ORGANIC AMMONIUM PERHALIDES, Ser. No. 211,362, U.S. Pat. No.4,886,915 filed herewith.

The solubility and bromine content of the compounds depend on the bulkand nature of the substituents. The most preferred substituents are R₁=hydroxyethyl, C₁ to C₈ alkyl groups, and R₂ =hydrogen, hydroxyethyl, orC₁ to C₈ alkyl groups.

In general, the compounds used in accordance with the method of thisinvention are mono- and di-substituted perhalides where X may bechlorine or iodine. It is preferred, however, to employ compounds whereX is bromine, that is, perbromides of the formula R₁ R₂ NH₂ --Br₃.

Specific stable, water soluble perhalides useful with the method of thepresent invention include ethanolammonium perbromide, propylammoniumperbromide, diethanolammonium perbromide, butylammonium perbromide,methylethanolammonium per bromide, ethylethanolammonium perbromide,hexylammonium perbromide octylammonium perbromide, dipropylammoniumperbromide, dibutylammonium perbromide, diethylammonium perbromide,1,6-hexanediammonium perbromide, as well as the corresponding chloro-and iodo-dibromides.

Ethanolammonium perbromide, HO--C₂ H₄ --NH₃ Br₃, is the preferred watersoluble organic ammonium perhalide in accordance with this invention.

Bromine is the active biocidal species in organic ammonium perbromides.It forms HOBr in the bulk water system to serve as the primary biocide.The uniqueness of these compounds is that the organic carrier serves asa solubilizer, allowing more bromine in the water to serve as a biocide.The complex formed also reduces vapor pressure, highly corrosive andtoxic vapors and reduces severe skin contact burns that exist withbromine alone. The combination of the HBr serves as a pH stabilizer inthe recirculating system. This helps keep water conditions morefavorable (i.e., lower pH) for the formation of the more efficaciousbiocidal product HOBr. (Basic conditions lead to OBr formation which isa less efficient biocide).

The method of the present invention involves the use of organic ammoniumperhalides as biocidal agents for selectively controlling bacterialgrowth in cooling tower and water recirculating systems. Typically,organic ammonium perhalides may be pumped into the recirculating waterof the system or simply introduced in measured amounts by hand into thesystem.

Because of their excellent water solubility, organic ammonium perhalidesmay be fed in systems in a relatively easy fashion. It is necessary toincorporate compatible materials of construction into the feed systemswith organic ammonium perhalides due to their strong oxidizing nature.Materials such as engineered plastics may be suitably used. Thefollowing equipment is understood well, is inexpensive and commerciallyviable for feeding liquid biocidal products.

1. Liquid Metering Pump

2. Eductors

3. Simply pour out of bottle.

4. Gravity Feed

5. Drip In

6. Spray

Products such as dipropylammonium perbromide, dibutylammonium perbromideand diethylammonium perbromide, which are partially soluble in water orare soluble solids, may be fed with the same methods but requireadditional dissolving time prior to use.

Automated control systems that measure bromine residuals may also beincorporated with this product to very accurately control feed withinspecific residual ranges. The agent may be fed in bulk water or into aside-stream.

By way of example, the reaction of ethanolammonium perbromide in wateris as follows:

    HO--C.sub.2 H.sub.4 --NH.sub.3 Br.sub.3 +H.sub.2 O→HO--C.sub.2 H.sub.4 --NH.sub.3 Br+HOBr+H Br.

Organic ammonium perhalides exhibit:

(1) Excellent shelf life stability;

(2) Easy dispersability and solubiliity in water;

(3) Easy use with commercially available plastic head pumps and eductorsand other low cost equipment.

In all cases, the presence of organic ammonium perhalides in therecirculating water acts as an effective biocide agent for controllingthe growth of various bacteria on the surfaces of the recirculatingwater systems.

The amount of added organic ammonium perhalides necessary for adequatebacterial growth control is dependent upon a number of factors, amongwhich include the volume of the recirculating system and the temperatureand pH of the water therein, the location of the system (i.e., is thesystem located in an area where bacterial nutrients may easily enter thesystem), quality of make-up water, and the amount of bacterial growthpresent at the time treatment is started.

Thus, for a new recirculating system one may easily control bacterialgrowth by simply adding an amount of organic ammonium perhalide to thewater and observing the results. That is, if after a period of timethere is an observed build up of algae, bacteria, etc., the amount oforganic ammonium perhalides should be increased. If there is no suchbuild-up, the quantity of organic ammonium perhalide added may bereduced until an accumulation of bacteria is noted, at which time theorganic ammonium perhalide level may be increased. Thus, through aseries of "trial and error" tests the preferred quantity of organicammonium perhalide needed for biomass control for any system can beeasily established.

Generally organic ammonium perhalide is provided in sufficient quantityso that at least about 0.005 pound of agent is provided daily perthousand gallons of water in the system. In determining the properamount of organic ammonium perhalide to be used, system volume is firstascertained. In the case of an open recirculating water system, systemvolume is normally calculated based on the amount of contained waterplus daily make up for evaporation losses and daily blow down. Once thetotal volume is determined, the appropriate agent level may be selected,with the final level being optimized on a step-by-step basis in thedescribed manner.

Preferably, organic ammonium perhalide is provided at a level lying inthe range of about 0.01 to about 0.12 pounds per thousand gallons perday. The benefits of this invention may be achieved with larger amountsof agent (e.g., at levels as high as 0.6 pound per 1000 gallons of wateror higher) although such higher quantities are typically only requiredwhere the system is quite dirty and then only for a relatively shortperiod of time (e.g.. a few days to a few weeks).

Organic ammonium perhalide can also be applied very efficiently on ashock basis. Typical recommendations are to feed product for one hourintervals, 2 to 3 times per day. The main purpose of shock feeding is touse less chemical while maintaining an ever decreasing biocount. Organicammonium perhalides can be provided at a rate lying in the range ofabout 0.6 to 7.2 lbs. per hour for every 1,000 gpm of flowing water. Asneeded, levels can be as high as 36 lb/hr for each 1000 gpm.

Ordinarily, biofouling is controlled by retaining a measurable halogenresidual in the recirculating water (all day or for shocking interval)and without complete destruction of all microorganisms in the bulk waterphase.

Unlike other water treatment environments such as swimming pools and thelike, biocidal effectiveness in cooling tower and water recirculatingsystems is not dependent upon a complete biological kill of allmicroorganisms existing within the recirculating water. Rather, incooling tower and water recirculating systems, it has been found inaccordance with this invention that it is only necessary tosubstantially kill the microorganisms which adhere to the walls andother film forming structural surfaces of the system. Once suchlocalized organisms are killed, the total microorganism count in therecirculating water is essentially irrelevant to the efficacy of thewater treatment method; that is, as long as the microorganisms are incirculation in the system (i.e., not adhering to the walls or otherstructural surfaces of the system), there is no noticeable detrimentaleffect on the heat-exchange capacity of the system.

As a result, the novel method of the present invention does not have asits objective the complete eradication of all microorganisms from therecirculating water but, instead, is intended to remove microorganismgrowth and biofilm from the surfaces of the recirculating water system.Thus, the term "biocidally effective" as used herein should beunderstood to refer to the selective attack on biofilmforming organismslocated at system surfaces but should not be understood to mean thesubstantial elimination of bulk water phase microorganisms. Otherapplications of the process of this invention include disinfection andother biological control of aqueous systems in the industrial andconsumer home use, as follows:

INDUSTRIAL APPLICATIONS

Recirculating cooling water

Once-through cooling water

Wastewater

Brewery pasteurizer water

Air washer water

Evaporative cooling water

Air scrubber systems

Humidifier systems

Oilfield injection water

Pond and lagoon water

Degreaser disinfectants

Closed cooling system water

Irrigation system disinfection

Metal working system disinfection

Food plant disinfection

Bleaching--pulp and paper

Textile

Metal etching

Metal extraction.

CONSUMER APPLICATIONS

Toilet bowl cleaners/disinfectants

Hard surface cleaners/disinfectants

Air conditioning pan water

Decorative fountain water

Tile and group cleaners

Bleaching agent compositions

Dishwashing formulation

Laundry formulation

Pool biocontrol/disinfection

Spas and hot tub biocontrol/disinfection

Thus, the term "aqueous system" as used herein encompasses all suchsystems.

Ethanolammonium perbromide and other organic ammonium perbromides can beused in different forms to meet various application criteria. Forexample, dilution with variable amounts of water, bases, acids,surfactants, salts, etc. and other solvents gives unique characteristicsto the product to make a lower vapor pressure, reduce potency, make iteasier to handle and stabilize.

In addition, stabilized aqueous solutions of the type disclosed in thecopending Favstritsky application may also be employed. Thus, when thecorresponding mono- or di-substituted ammonium hydrohalide, R₁ R₂ NH₂ X,where R₁, R₂ and X are as previously defined, are mixed in aqueoussolution with one mole of bromine, stabilized aqueous perbromidecompositions are obtained. Shelf life stability of such aqueoussolutions may also be enhanced by replacing a portion of the hydrohalidewith an alkali metal or ammonium bromide stabilizing salt, especiallysodium bromide or ammonium bromide. Preferably, the ratio of hydrohalideto other salt is abaout 1:1.

The agents of this invention may also be mixed with other active agentssuch as algacides, fungicides, corrosion inhibitors, scale inhibitors,nonoxidizing biocides and other compatible products which will lendgreater functionality to the product. If soluble with the agents of thisinvention, such other additives may be incorporated in the same feedsystem. Insoluble products may be fed in a separate manner, or otheradditives can be incorporated to increase solubility.

EXPERIMENTAL EVALUATIONS

In order to establish the effectiveness of organic ammonium perhalidesas water treatment biocides, biocidal agents, a series of tests havebeen performed. These tests document the use of organic ammoniumperhalides in various sizes and types of cooling towers and waterrecirculating systems. Where practical, tests have been performed onsimilar cooling tower systems using BCDMH as a biocide so that acomparison of biocidal effectiveness with that known biocide can bemade.

Other tests compare the biocidal efficacy of the family of perbromidesvs. various organisms. P. aeruginosa is the primary bacteria of concernin recirculating systems. Ethanolammonium perbromide showed 100T killvs. P. aeruginosa in 5 minutes @ 0.6 ppm Cl₂. The data are reported inTables 2 and 3 for ethanol ammonium bromide ("EAPB"): propylammoniumperbromide ("PAPB"): and diethanolammonium perbromide (DEAPB").

                  TABLE 2                                                         ______________________________________                                        Polyhalides vs. P. aeruginosa                                                                 Measured Free                                                        mg       Halogen     Measured Total                                                                           Time                                          Sample/  Residual    Halogen Residual                                                                         to                                     CPD    L H.sub.2 O                                                                            as Cl.sub.2 as Cl.sub.2                                                                              Kill                                   ______________________________________                                        PAPB   1.9      0.18 ppm    0.33 ppm   10 min.                                EAPB   1.76     0.21 ppm    0.29 ppm   10 min.                                DEAPB  1.71     0.32 ppm    0.34 ppm   10 min.                                ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Inhibition of Growth                                                                      ppm    % Inhibition of Growth                                     Organism Type     Product  PAPB   EAPB  DEAPB                                 ______________________________________                                        Klebsiella                                                                             Bacteria 20       76     92    81                                    pneumoniae                                                                    Pseudomonas                                                                            Bacteria 20       95     99    99                                    aeruginosa                                                                    Bacillus Bacteria 20       61     99    97                                    megaterium                                                                    Trichodema                                                                             Fungus   20        2     15    16                                    viride                                                                        Chorella Algae    10       27     53    29                                    pyrenoidosa                                                                   ______________________________________                                         ##STR4##                                                                 

The efficacy of the organic ammonium perhalides of the invention hasbeen demonstrated by the following examples.

EXAMPLE 1 Cooling Tower 1

Single Cooling Tower

Contained Volume: 15,000 gallons

Circulation Rate: 100 gpm.

This tower was controlled on a low level BCDMH feed. EAPB was shock fed(i.e.. adding high dose of product and turning off to allow biocide todo its job) periodically over an 8 hour day. All total halogen wasdetected based on feed amount and theoretical expected. Data arereported in Table 4.

                  TABLE 4                                                         ______________________________________                                        Example 1 Trial Data                                                          Product Feed           Total Halogen                                          Rate        Time       Measured as Cl.sub.2 (ppm)                             (ml/min)    (Hours)    Basin     Deck                                         ______________________________________                                        0.0         0.0 on     0.0                                                    15.0        0.08       11.75                                                  15.0        0.25       22.39                                                  15.0        0.50 off   40.05     30.10                                        0.0         1.0        23.75     24.10                                        0.0         1.5        20.27                                                  0.0         3.75        8.79      8.51                                        0.0         4.25 on     7.09                                                  1.5         4.58       9.7                                                    1.5         5.08       11.63                                                  1.5         5.5        12.05                                                  1.5         5.9        12.76                                                  1.5         6.2        12.90                                                  ______________________________________                                    

The system cleaned all biomass and sludge out based on high level feedand showed that EAPB is very effective as a quick shocker as well ascompletely miscible in water. Bromine residuals were generated in waterin accordance with its theoretical "load" of oxidizing halogen; theyield was very close to the expected amount. With respect to itsmicrobiological efficacy, bromine thus delivered is not distinguishablefrom that which is derived from inorganic sources. There is virtually nointerference in efficacy from the organic carriers at use-concentrationdilutions.

The concentrations of product required for efficacous application mustbe determined from the percent available bromine and knowledge of thehalogen demand in the system. Generally, a concentration of one ppm freeresidual bromine will disinfect (i.e., 99.9% kill in 10 minutes)laboratory strains of Pseudomonas aeruginosa. However, continuous-dosingat one to three ppm free residual bromine is recommended forapplications in which there is a constant influent source ofmicroorganisms, or in systems where biofilms are predominant.Slug-dosing treatment protocols are especially efficacous in troublesomesystems: the product water solubility allows for convenient application.Five ppm free residual bromine slug-doses for 1-2 hrs once per day arerecommended.

Based on this test, it was observed that:

1. EAPB is an efficient source of bromine, all bromine introduced intothe system could be accounted for due to its excellent water solubility.

2. EAPB could be easily dispensed by liquid pumps, commonly used inindustry, and a steady residual will be maintainable based on coolingtower size as well as system demand. No problems were seen from theslight vapor pressure the product possesses.

3. EAPB also has the advantage of being very effective as a shocktreatment.

4. At even the extreme levels run in this test, no foaming from theamine was evident.

EXAMPLE 2 Cooling Tower 2

Chemical Plant Tower:

Contained System Volume: 35,000 gallons

Circulation Rate: 1000 gpm.

This tower had previously been treated with BCDMH with about 11.5 poundsof product per day and an erratic residual Cl₂ control of 1.3 to 2.5ppm. (1 ppm BCDMH has a raw dose of 0.55 ppm active Cl₂) This high levelCl could lead to excessive corrosion as well as over use of biocide. TheEAPB controlled the system accurately at 0.05 to 0.4 ppm during its 6week trial at a feed of 6.1# or 0.4 gallons of product per day. (1 ppmethanolammonium perbromide has a raw dose of 0.181 Active Cl₂.) BCDMHcontrol was 1.7 mls/year for mild steel coupons. Data are given inTables 5 and 6.

                  TABLE 5                                                         ______________________________________                                        Average Background Conditions for Example 2                                                 BCDMH          EAPB                                             ______________________________________                                        Daily Water     4,800            17,000                                       Use (gallons)                                                                 Calcium (ppm)   76               103                                          Alkalinity      71               43                                           Conductivity    496              630                                          Phosphate (ppm) 17               10                                           Bromide (ppm)   26               80                                           Chloride (ppm)  31               23                                           TOC (ppm)       61               --                                           DMH (ppm)       73               --                                           pH              7.7              7.1 -Free Cl.sub.2 (ppm)                                                             0.6  0.10                             Total Cl.sub.2 (ppm)                                                                          1.63             0.14                                         Colony Counts   <10.sup.3        10.sup.5                                     lbs/Day Feed    8.6              6.1                                          Avg. Dosage                                                                   (ppm Cl.sub.2)  118 ppm   7.8 ppm                                             ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        Example 2 Trial Data                                                                               Colony          Colony                                   Day          (ppm)   Counts    (ppm) Counts                                   ______________________________________                                         1           1.33     10.sup.3 0.31  10.sup.4                                  2           1.45    <10.sup.3 0.27  10.sup.4                                  3           1.15     10.sup.3 0.36  10.sup.3                                  4           1.54    <10.sup.3 0.20  10.sup.4                                  5           1.31     10.sup.3 0.21  10.sup.4                                  6           1.88    <10.sup.3 0.24  10.sup.5                                  7           2.53    <10.sup.3 0.23  10.sup.5                                  8           1.70    <10.sup.3 0.22  10.sup.5                                  9           1.77    <10.sup.3 0.06  10.sup.5                                 10           1.97    <10.sup.3 0.12  10.sup.5                                 11           1.50    <10.sup.3 0.22  10.sup.5                                 12           1.54    <10.sup.3 0.13  10.sup.5                                 13           1.50     10.sup.3 0.07  10.sup.5                                 14                             0.04  10.sup.5                                 15                             0.05  10.sup.5                                 16                             0.05  10.sup.5                                 17                             0.06  10.sup.5                                 18                             0.05  10.sup.5                                 19                             0.04  10.sup.5                                 20                             0.08  10.sup.4                                 21                             0.11  10.sup.4                                 22                             0.05  10.sup.6                                 23                             0.11  10.sup.6                                 Average      1.63    <10.sup.3 0.14  10.sup.5                                 Dose (lbs./day)                                                                            8.6               6.1                                            ______________________________________                                    

A second test was performed at the end of the trial to increase feed ofEAPB and an increased biocontrol was achieved as expected, as reportedin Table 7. Colony counts (count bacteria/ml) were determined usingSelecticult dip slide culture tests, a commercially available test formonitoring and enumerating microbiol densities in industrial fluids.

                  TABLE 7                                                         ______________________________________                                        Increase of EAPB Dosage for Example 2                                                  Dose   Total Cl.sub.2                                                                         Colony Counts                                        Day   Hour     (lb/day) (ppm)  Hot Side                                                                             Tower Deck                              ______________________________________                                        23     1 am     6.1     .06    10.sup.6                                                                             10.sup.5                                       4 am     6.1     .11                                                          8 am     6.1     .12                                                         12 am     6.1     .13                                                          2 pm    16.5     .17    10.sup.5                                                                             10.sup.4                                       4 pm    16.5     .19    10.sup.5                                                                             10.sup.4                                       8 pm    16.5     .24                                                         12 pm    16.5     .27                                                          4 am    16.5     .29                                                          8 am    16.5     .30    10.sup.6                                                                             10.sup.4                                      10 am    27.6     .30    10.sup.5                                                                             10.sup.4                                      12 am    27.6     .33    10.sup.5                                                                             10.sup.4                                       4 pm    27.6     .33    10.sup.5                                                                             10.sup.4                                       8 pm    27.6     .36                                                         12 pm    27.6     .42                                                          4 am    27.6     .36    10.sup.4                                                                             10.sup.4                                       8 am    27.6     .42                                                   ______________________________________                                    

I claim:
 1. A method for controlling biofouling in an aqueous systemcomprising the steps of:introducing a water soluble ammonium perhalideof the formula: ##STR5## where R₁ and R₂ are independently hydrogen,hydroxyethyl, alkyl, cycloalkyl, alkyl ether, polyoxyalkylene, andhalogenated alkyl; X is chlorine, bromine or iodine; n is 2 to 6; andonly one of R₁ and R₂ may be hydrogen, into the system at a frequency,duration and concentration sufficient to control biofouling in thesystem.
 2. A method, as claimed in claim 1, wherein X is bromine.
 3. Amethod, as claimed in claim 2, wherein R₁ is a member selected from thegroup consisting of hydrogen, hydroxyethyl and C₁₋₈ alkyl and R₂ is amember selected from the group consisting of hydroxyethyl and C₁₋₈alkyl.
 4. A method, as claimed in claim 1, wherein the perhalide isethanolammonium perbromide, HOCH₂ CH₂ NH₃ --Br₃.
 5. A method, as claimedin claim 1, wherein the perhalide is propylammonium perbromide, CH₃ CH₂CH₂ NH₃ --Br₃.
 6. A method, as claimed in claim 1, wherein the perhalideis diethanolammonium perbromide, (HOCH₂ CH₂)₂ NH₂ --Br₃.
 7. A method, asclaimed in claim 1, wherein the aqueous system is a recirculating watersystem.
 8. A method, as claimed in claim 7, wherein the water solubleammonium perhalide is provided at a level of at least about 0.005 poundsper thousand gallons of water per day.
 9. A method, as claimed in claim8, wherein the perhalide is provided at a level of about 0.01 to 0.6pounds per thousand gallons per day.
 10. A method, as claimed in claim8, wherein the aqueous system is shock treated by periodically providingwater soluble ammonium perbromide at a rate of about 0.6 to 36 poundsper hour per thousand gallons per minute of flowing water.